The invention discloses a plating solution for plating copper on a carbon nano tube. The plating solution specifically consists of the components: 5-50g/L of copper salt, 0.1-1.5g/L of grain refiner, 5-50g/L of complexing agent and the balance water. The plating solution simply consists of the copper salt, the grain refiner and the complexing agent, and is simple in formula; with the adoption of the plating solution having the specific components and a specific matching ratio, the surface of the carbon nano tube can be coated with nano copper grains very uniformly, and the grain sizes of the nano copper grains coating the surface of the carbon nano tube are 34-38 nanometers.